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bciskepottery

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Everything posted by bciskepottery

  1. A somewhat long missive. If you get the opportunity to take a workshop with Akira, I highly recommend it. His workshops are hands-on and he is very generous with his knowledge of technique and craftsmanship. First, here is Akira's slip recipe: Goldart, 6 lbs. (30%) Kaolin - EPK, 10 lbs. (50%) [Akira also uses Grolleg or Tile 6 for a whiter slip and Helmar for woodfired items] Custer Feldspar, 2 lbs. (10%) Silica, 2 lbs. (10%) His recipe makes a five-gallon bucket of slip; I usually half the quantity and make a smaller 2 1/2 gallon bucket. For the 2 1/2 gallon bucket, I add between 4 and 4 1/2 quarts of water; for a five-gallon bucket, add 8 to 9 quarts. I generally hold off on the last quart, adding a bit at a time to get the right consistency. This will be a thicker slip than you are probably used to making -- almost yogurt consistency. I've found that leaving it a bit on the thicker side and then adding some water as needed is better than making it too thin and watery. After mixing, it is sieve time (30 or 40 mesh should be fine); this is somewhat labor intensive but the creamy slip you get as a result is well worth the effort. I let the bucket stand overnight and remove any excess water that rises to the top of the bucket. Recently, I tried using Grolleg instead of EPK and it worked fine; fired a little whiter, which was expected. For clay bodies, I've used Standard 153 (^10), Laguna Dark Brown (which fires to black at ^10), and Highwater Hestia (^10) that is fired in reduction. I've played with a couple items at ^6 using Standard 266 and Highwater's Red Rock that is fired in my electric kiln. So, start with a slab . . . either from a slab roller or made by hand. I use a slab roller because I vary the thickness of the slab just a bit depending on what I plan to make. For things like boxes and ikebana vases, I prefer a thicker slab to start as it allows for a wider edge seam for joining (I use a 45 degree bevel cutter). Also, as described below, when you stretch the slabs after the slip firms up, the slab compresses and becomes thinner. So, you want to allow for that compression at the outset. I generally set the slab roller for a generous 1/4 inch slab for general items and between 1/4 and 3/8 inches for boxes. My slab sizes generally run 12"x15" (my slab roller is small); I've found that to be a good size for doing the stretch part described below. I place a couple sheets of newspaper on a table and then set the slab(s) on top of the newspaper. On top of your slab, add about 1/3 to 1/2 cup slip. Glop it in the middle and spread it around evenly -- I use a three-inch spackling knife (you can also use a wide hake brush); don't worry about going over the ends of the slab. At this point, just try to even out the slip, don't worry about the surface. (If you want to do some very precise patterns, like the seashell Akira uses on his teapots, use less slip or a thinner slip.) After allowing the slip some time to settle -- maybe 30 minutes, I go back with a second brush to make my final pattern. Lately, I've been use a stiff brush . . . a basting brush from the kitchen. Using that brush, I make my patterns . . . generally just a fluid arm (not wrist) movement from right to left, left to right, starting at the top and working toward the bottom. You can criss cross or just make parallel lines. If there is too much slip building up on the brush, remove it and continue. At this point, the brush lines will begin to develop; work (but don't overwork) until you see a pattern that you like. If you work it too long, the slip will become less thick and flatten. At this point, you need to let the slab set . . . I can leave mine out overnight in the studio; how long this takes will depend on temperature and humidity (during the DC summer, it can set in a few hours; during the winter, I've let them set out a couple days in the garage studio). You want the slab to get about medium leather hard. Too soft and the slip will not create the breaks you want when the slab is stretched; too hard, the slab will crack and tear. If the slab does dry faster than you thought, you can use a water spritzer to rehydrate the slab (spritz both front and back to restore even moisture). If you can bend the slab and the slip does nothing, its too soft; if you bend the slab and it breaks, too hard. Once the slab is set up, the next step is to stretch it. This is how Akira creates those beautiful patterns. For stretching, gently toss the slab across a plain piece of unfinished plywood, 24"x24"x3/8". First, I drop the slab on the plywood from a height of about 12 inches (just a plain pancake drop). . . this wakes up the clay. Then I turn the clay over so the slip is face down on a piece of thin foam. I take a cardboard tube . . . mine are the tubes from rolls of shrink-wrap, about 4" or so in diameter (you could substitute a piece of PVC wrapped in newspaper so the clay won't stick) and if roll the slab around the tube. This helps break the slip along its texture lines and also begins to give the slab memory of being a curved surface and not flat slab. [if you are not doing round work, no need for this step.] Remove the slab from the tube and place it slip-side up on the plywood. The next step is stretch the slab. To do this, pick up the slab by the sides and gently toss it -- at an angle -- against the plywood slab so that the slab stretches as it strikes the surface of the wood. I generally hold the slab in my outstretched arms and toss it at an angle towards me. Rotate the slab 180 degrees, and repeat. With each strike against the plywood, you will begin to see the slip stretch and pull away from the underlying clay slab. Repeat until you get the look you like but don't get greedy . . . too much stretching and the slab will tear or it will compress unevenly. This is the hardest part of the process and it takes some time to get a feel for doing. I've noticed a tendency for slabs to thin more in the middle and tear along the edges if you stretch it too many times. Once you've gotten this far, your slab is ready and you can make whatever form you want. If the slab is very pliable, you can let it set up for a while. For joining edges, Akira uses an overlap technique where he takes a rasp (Sherrill's Mud Tool rasp) and shaves down opposite sides about 1 inch, then scores and adds slip to join. Basically, you want the thickness of the join to be the same as the thickness of the slab wall . . . if it is thicker, it can distort while drying. Bisque firing is your usual bisque firing. Once bisqued, Akira applies a red iron oxide wash to the vessels and sponges off the wash from the high areas of the surface, leaving the RIO to penetrate into the exposed clay body. I've used straight RIO and water, as well as a combination of RIO, Frit 3124, and water. Insides are glazed -- he seems to favor shino or iron red, but its really up to you. Akira fires in reduction to cone 10 in either his diesel fueled kiln. I fire my kohiki work in reduction in a natural gas kiln. I've been trying to get a similar look in an electric kiln by applying a soda ash wash to the outside to get a similar sheen on the slip; I'm not quite there yet. The two keys seem to be catching the slab at the right time to begin stretching, and then stretching itself to get the slip to break and expose the underlying clay body. When I do kohiki, I'll make 6 or 8 slabs at a time, fills up a 6' folding table top. Once stretched, I'll store them in a plastic bin, with sheets of plastic separating each slab, to keep them moist while building various boxes, bottles, vases, etc. The process is a bit time consuming, but well worth the effort, in my opinion. And, I've adapted and added to what Akira taught in the workshop. Right now, I'm trying thicker slip applications so the surface is more 3-D feeling.
  2. bciskepottery

    Looking for Raku Class in Santa Fe

    Try Taos Clay Studio . . . just up the road. They have a workshop option that might work.
  3. bciskepottery

    Ways To Make Square Forms\Urns

    I use a wire cutting tool to make 45 degree beveled edges on my slabs, score the edges, and assemble. Use the triangle piece cut from the edge on the inside to strengthen the corner, or a thin coil. For boxes with tops, I follow Min's process -- make the box, let it set up, then cut the top part off. On the inside of the bottom part, I add some thin slaps to serve as a gallery or sorts.
  4. bciskepottery

    What are cone temperatures

    Good starting point for understanding cones: Use cones to make sure your digital controller is accurate and validate its temperatures. Like an insurance policy.
  5. bciskepottery

    Bloaty Mc-Bloatface

    At one point, we were all beginners and newbies. Min and the others have given some good advice. On your bloating, does it happen throughout the kiln, or just top, bottom, or middle? Does your kiln have one thermocouple or three? Sounds like one -- which means your kiln controller is measuring its firing temperature at the middle of the kiln (also called one zone). To compensate for unevenness in temperature, the manufacturer will alter the elements for top and bottom to heat differently than the middle -- all part of their design to even out the firing. A kiln with multiple thermocouples typically measures top, middle, bottom and adjusts element heating accordingly. The cones will tell/confirm where your cool spots are. Then comes the fun part of figuring how to load your kiln to balance the heat and reduce/minimize the cools and hot spots. For bisque, if you are firing bone dry wares, no need to keep the top open -- especially if your kiln has a vent system. If no vent, some leave the kiln top slightly open, then drop it at 1000F. That allows any steam from physical and chemical water to escape. When I fired kilns for a community studio, we did a preheat because we were dealing with a wide range of work, some thick, some thin, some bone dry for weeks, some on the shelf that morning. That was a precaution for us. In my own studio, I know my work is dry, no preheat. For glaze loads, drop the top. My kiln top rises slightly during firing (1/8 to 1/4 inch) because air in the kiln expands as it heats. That is normal. If the lid does not sit flush when not on, or rises a lot -- more than 1/2 inch, you will need to adjust the hinge -- as Min suggested.
  6. bciskepottery

    Glaze Application Questions.

    Applying glazes takes practice; you should get better over time. Unfortunately, there may be many pieces made, glazed before you get the technique down. But I've found that is a learned skill. As many potters will have as many tricks of the trade they've developed. You sound like you have the basics (although I'm a three or four second dipper); just make pieces and practice. The part of potting that most "hate" is glazing, because it doesn't turn out the way you envisioned the glaze. But you'll get there. Some glazes are very sensitive to glaze thickness, so even rubbing down a drop on a tong mark or finger mark will leave a trace. I've use an artists paint brush to dab tong marks, let it dry, and then smooth it down until it matches the rest of the glaze thickness. Some leave the marks and let the glaze melt cover them, especially if the glaze tends to move while firing. Some glazes show those marks more than others. Spraying leaves no tong marks, but takes longer (and has a good learning curve to get right thickness).
  7. bciskepottery

    Artspeak

    http://www.pixmaven.com/phrase_generator.html
  8. bciskepottery

    Locally Made-get on the bandwagon

    Yep, locally made . . . with glaze ingredients/oxides mined from Africa, kaolins imported from New Zealand, feldspars from England and Spain, etc. etc. etc. And don't forget to support your local artists . . . who are more than willing to sell/ship world-wide from his/her Etsy/Amazon/personal web site. I associate the word "bandwagon" with fleeting supporters/fans who join the latest fashion or fad. Give me long-term, loyal customers who buy regardless of trends. (Just feeling the irony today). ; )
  9. bciskepottery

    in search of these tile hooks

    https://www.amazon.com/dp/B019QX7CY8/ref=asc_df_B019QX7CY85233239/?tag=hyprod-20&creative=395033&creativeASIN=B019QX7CY8&linkCode=df0&hvadid=193166724913&hvpos=1o1&hvnetw=g&hvrand=1972749360143774791&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9008188&hvtargid=pla-362684347567
  10. bciskepottery

    Recommended electric potter's wheel

    I am not a "big" thrower; on those really rare occasions when I do make a big item, I take the Tony Clennell approach and throw in sections . . . 8 to 12 lbs. or so. At those weights, torque is no problem. Coning, centering, and throwing 25 lbs. or so takes strength I just don't have at my age. I had an instructor who would occasionally throw a demo with 25 lbs. -- and he would collapse the ware at the end of class.
  11. bciskepottery

    Recommended electric potter's wheel

    I have a Shimpo Whisper VL. Love it. Learned on Brents in a community studio that also had some old Shimpos and found the Shimpo foot pedal more responsive. Direct drive means fewer moving parts to replace down the road. Had I not gotten the Shimpo, I would have gone with either the Thomas Stuart (pre-bought out by Skutt) or the Bailey Pro.
  12. If you are up for testing, consider letting the half pint dry out into powder, then reconstitute with water (no gum). Then treat as a dipping glaze, like the undercoat of obsidian.
  13. Can you also get the second glaze in powder form to mix? That avoids the whole no-gum/gum situation.
  14. bciskepottery

    colouring large batches of porcelain

    One thing to check out is if you can get your clay dry, not already mixed. That eliminates the need to dry it out to get a powdered form. Many clay manufacturers sell their clay dry.
  15. bciskepottery

    Kiln Install on Deck

    Durock cement board is described as mold and water resistant . . . and there's a difference between water resistant and water-proof. Cement board is generally used as a backing, not an exposed surface.
  16. bciskepottery

    Kiln Install on Deck

    Looks like we need to step back and take a deep breath . . . It is okay to respectfully disagree or challenge on content, but let's avoid making comments that characterize members personally. That is not what the Forum is about. And, I'm not singling out this thread . . . it has also occurred in some other recent ones. We all bring different strengths -- whether experience, education, or whatever -- to the discussions and all of our members, whether professionals, students, or newbies, benefit from those strengths. Sputty's comment is accurate regarding the auto-ignition point of wood. And the suggestion of a layer of bricks with aluminum foil is a valid one -- it would satisfy the manufacturer's suggestions listed by Neil. One clarification I'd like to see is whether Sputty's kiln is sitting directly on the OSB floor or if there is a layer of bricks/stand that separates the kiln floor from the OSB floor. One clarification I'd like to see is whether the Milwaukee fire cited by Neil involved a kiln directly on the floor or if it was raised above the wood floor with a stand or layers of brick or other materials.
  17. bciskepottery

    Food Coloring - dying glazes for better application.

    I use food coloring for wax -- few drops of green. Just burns out without a trace. Might be a good starting point.
  18. bciskepottery

    Dipping Bisque into Clear Glaze

    How are you prepping your bisque for glaze application? Wiping with a damp sponge? Any possibility you might have dust, oil from skin, or something else on surface of bisque?
  19. bciskepottery

    Firing An Accidentally Glazed Green Ware Pot?

    Different glaze application techniques will make a difference. When you spray, more glaze and less water goes on the ware -- so dry pieces mostly get glaze and not water. If you dip, you will have to deal with more water and will need to dip at a stage where adding that much water would not affect the ware.
  20. bciskepottery

    Pkqw #24

    Week 24 Note from Pres: The questions this week are taken from an older book. The book is about electric kiln ceramics, and unless otherwise stated, assume an electric kiln when talking about firings. The main alternative to creating and reducing atmosphere in the kiln is to add reducing materials to the glaze. Several materials are available but by far the most useful and one with the author has experimented is _____________________. bone ash soda ash silicon cabide sodium silicate To fit well, both before, during and after firing, body and glaze must expand and contract at much the _______________________ and to much the same extent. same rate differing rate same hardness none of the above One method of joining together a burnt-out element. Stretch the wire and interlock; dab the join with ___________. Turn on the electricity supply , which will cause the wire to arc at the joins and fuse together. Kiln cement oil water super glue A _______________ glaze develops because the glaze contracts when cooling more than the body, this can happen with shiny or matt, colored or clear glazes. Glossy Lava Matt Crackle This weeks questions come from Electric Kiln Pottery-The Complete Guide, by Emmanuel Cooper, c. 1982, Anchor Press for B.T. Batsford Ltd. Note from Pres: A much older book that helped me years ago to explore cone 6. This was the first book I was aware of at the time that had a full chapter on Cone 6 Ceramics, and glaze recipes of which Floating Blue was on I first used. Answers: 3. Silicone Carbide-The main alternative to creating a reducing atmosphere in the kiln is to add reducing materials to the glaze. Several materials are available but by far the most useful and one with which I have experimented is silicon carbide (SiC) better known as carborundum. 1. same rate-Here the problem is to achieve a good fit between body and slip. Shrinkage has to be much the same and a good bond has to form between body and slip. 3. water-One method of joining together a burnt-out element. Stretch the wire and interlock; dab the join with water Turn on the electricity supply, which will cause the wire to arc at the joins and to fuse together 4. Crackle-The development of craze lines in the glaze which are recognized as a decorative feature are known as crackle glazes. . . .. On pots intended for functional use such a crackle creates both a poor bond between body and glaze, which makes it physically weak, and a trap which can hold food and make it unhygienic. For these reasons crackle glazes are best reserved for use on decorative pieces. A crackle develops because the glaze contracts when cooling more than the body, and this can happen with shiny or matt, colored or clear glazes.
  21. bciskepottery

    Is Patsy Green 2 From Britt Book Food Safe?

    Whether 1 foot x 120 feet or 15 feet x 120 feet, they are all billable hours. And the more lawyers involved, the more hours billed. (Full disclosure: my daughter is a law school graduate, I work with an agency full of lawyers, and am a consultant who bills by the hour.)
  22. bciskepottery

    Is Patsy Green 2 From Britt Book Food Safe?

    I think a main concern about leeching is that it could affect the taste or appearance of the food coming in contact with it. Also, there can be some discoloration of the surface of the ware. Hesselberth and Roy adopted limits leeching for U.S. drinking water (I think) because there are no standards (except for wares used in commercial eateries that are issued by FDA). And, if you look at limits between H & R, Britt, Tony at Digitalfire, and others, there are variances in what they recommend. H&R focused on durability, so their limits reflected that emphasis.
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